How we work this out

Kīlauea's been erupting in short "episodes" of lava fountaining since December 23, 2024. Whether you see one is mostly about timing. We separate two different sights so the headline is honest:

Night glow happens most evenings — even during pauses — and weather is the main thing limiting it. Active lava fountaining is rare (hours long, roughly weekly). The hero percentage is the chance of fountains on your day; glow is shown separately, in words.

How the number is built

Every 15 minutes we read HVO's official notices. Status Reports tell us exactly when each fountaining episode started and ended; the Daily Update tells us HVO's forecast window for the next one. New eruptions flow into the site automatically.
We then simulate thousands of plausible futures for the eruption. The next episode's start time blends HVO's window (when one is published) with the rhythm of past pauses — weighted toward the recent, faster cadence — and always accounts for the fact that nothing has erupted yet as of right now.
Each day's number is simply the share of those simulated futures in which fountains are active at some point that day (Hawaiʻi time). Later episodes spread wider and fade as uncertainty piles up — distant peaks are softer, not sharp promises.
For a whole trip we count the share of simulated futures in which at least one episode overlaps your dates. That's exactly consistent with the per-day numbers, and a longer stay that covers more of the cycle honestly gives you a better shot.
The further out the date, the less we claim. For dates beyond a few weeks we show the typical rhythm and ask you to check back. Eruption behavior could also change — HVO is explicit that its forecast ability ends if Kīlauea starts behaving differently, and so does ours.

Where the data comes from

This site is not an official or emergency service. Always defer to USGS alerts and Hawaiʻi County Civil Defense.